This invention relates to polyolefin compositions having stability against degradation caused by exposure to heat and oxygen, especially in the presence of copper.
It is well known in the art to stabilize polymers against degradation due to heat and oxidation by incorporating into the polymers a stabilizing amount of hindered phenolic antioxidants, e.g. those disclosed in U.S. Pat. Nos. 2,968,644 and 3,285,855. However a serious disadvantage to the use of plastic materials, such as polyolefin resins, as insulation for wire and cables is the fact that the degradation of the polymer is accelerated by the presence of copper and alloys of copper. Prior art methods to solve this problem have resulted in a combination of the polyolefin resins with the primary hindered phenolic antioxidant and a copper deactivator or chelating agent such as certain organic hydrazide or hydrazine compounds, e.g. those disclosed in U.S. Pat. Nos. 3,438,935; 3,484,285; 3,752,865; and 3,772,245.